Hydrogen gas filling method and hydrogen gas filling device

ABSTRACT

According to one aspect of the present invention, a hydrogen gas filling method includes receiving, from a vehicle equipped with a tank to be filled with hydrogen gas and powered by the hydrogen gas, a temperature of the tank before a start of filling; calculating a difference between a preset maximum temperature and the temperature of the tank; calculating a filling speed of the hydrogen gas depending on the difference; and filling the hydrogen gas from an accumulator in which the hydrogen gas is accumulated into the tank at the filling speed calculated via a measuring machine.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation application based upon and claims thebenefit of priority from prior Japanese Patent Application No.2018-102762 (application number) filed on May 29, 2018 in Japan, andInternational Application PCT/JP2019/020894, the International FilingDate of which is May 27, 2019. The contents described in JP2018-102762and PCT/JP2019/020894 are incorporated in the present application.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to a hydrogen gas filling method and ahydrogen gas filling device, for example, a hydrogen gas filling methodand a hydrogen gas filling device for a vehicle powered by hydrogen gasat a hydrogen station.

Related Art

As fuel for vehicles, in addition to conventional fuel oils such asgasoline, recently, hydrogen fuel has attracted attention as a cleanenergy source. As a result, fuel cell vehicles (FCVs) powered by thehydrogen gas have been developed. In order to popularize the fuel cellvehicle (FCV), it is necessary to expand hydrogen stations capable ofrapidly filling the fuel cell vehicle with the hydrogen gas. At thehydrogen station, in order to rapidly fill the FCV with the hydrogengas, a multi-stage accumulator including a plurality of accumulators foraccumulating the hydrogen fuel compressed to a high pressure by acompressor is disposed. By performing filling via a dispenser (measuringmachine) while switching the accumulator to be used, a differentialpressure between a pressure inside the accumulator and a pressure of afuel tank of the FCV is greatly maintained, and the FCV is rapidlyfilled with the hydrogen gas by the differential pressure from theaccumulator to the fuel tank (for example, refer to JP-A-2015-197700).

Here, in the case of filling the hydrogen gas at the hydrogen station, afilling time until full filling is estimated by a simulation with alarge margin in advance for an actual temperature increase of the fueltank so that the temperature of the fuel tank of the FCV does not becomea high temperature, by using the hydrogen gas that is cooled enough toprevent the supply temperature of the hydrogen gas from increasing.Then, a filling speed is determined according to the estimated fillingtime. Therefore, the determined filling speed is generally set lower ascompared with the actual filling capacity of the hydrogen station.Therefore, a wasted filling time is required. Further, in order toprevent the supply temperature of the supplied hydrogen gas fromincreasing, a cooler (precooler) in the dispenser is constantly suppliedwith a refrigerant from a refrigerator, and the hydrogen gas is cooledto, for example, −40° C. Therefore, a large amount of electric power isrequired to circulate the refrigerant.

BRIEF SUMMARY OF THE INVENTION

According to one aspect of the present invention, a hydrogen gas fillingmethod includes

receiving, from a vehicle equipped with a tank to be filled withhydrogen gas and powered by the hydrogen gas, a temperature of the tankbefore a start of filling;

calculating a difference between a preset maximum temperature and thetemperature of the tank;

calculating a filling speed of the hydrogen gas depending on thedifference; and

filling the hydrogen gas from an accumulator in which the hydrogen gasis accumulated into the tank at the filling speed calculated via ameasuring machine.

According to another aspect of the present invention, a hydrogen gasfilling device includes

a reception circuit configured to receive, from a vehicle equipped witha tank to be filled with hydrogen gas and powered by the hydrogen gas, atemperature of the tank before a start of filling;

a difference calculation circuit configured to calculate a differencebetween a preset maximum temperature and the temperature of the tank;

a filling speed calculation circuit configured to calculate a fillingspeed of the hydrogen gas depending on the difference;

an accumulator configured to accumulate hydrogen gas; and

a measuring machine configured to fill hydrogen gas from the accumulatorinto the tank at the filling speed calculated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example of a configuration diagram showing a configurationof a hydrogen filling system of a hydrogen station in a firstembodiment.

FIG. 2 is a configuration diagram showing an example of an internalconfiguration of a control circuit that controls the entire hydrogenfilling system in First embodiment.

FIG. 3 is a flowchart showing main steps of a hydrogen filling method inthe first embodiment.

FIG. 4 is a diagram showing an example of a correlation between atemperature increase change of a fuel tank and a filling speed in thefirst embodiment.

FIG. 5 is a diagram illustrating a coefficient table of a quadraticpolynomial when the correlation between the temperature increase changeof the fuel tank and the filling speed is approximated by the quadraticpolynomial in the first embodiment.

FIG. 6 is a diagram showing another example of the correlation betweenthe temperature increase change of the fuel tank and the filling speedin the first embodiment.

FIG. 7 is a diagram illustrating a coefficient table of a cubicpolynomial when the correlation between the temperature increase changeof the fuel tank and the filling speed is approximated by the cubicpolynomial in the first embodiment.

FIG. 8 is a diagram illustrating a filling method in a case ofperforming differential pressure filling of hydrogen fuel by using amulti-stage accumulator in the first embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments below describe a method and a device capable of fillinghydrogen gas at a filling speed where an extra margin is eliminated, ina case that the hydrogen gas is filled.

First Embodiment

FIG. 1 is an example of a configuration diagram showing a configurationof a hydrogen filling system of a hydrogen station in a firstembodiment. In FIG. 1, a hydrogen filling system 500 is disposed in ahydrogen station 102. The hydrogen filling system 500 includes amulti-stage accumulator 101, a dispenser (measuring machine) 30, acompressor 40, a refrigerator 42, and a control circuit 100. Themulti-stage accumulator 101 includes a plurality of accumulators 10, 12,and 14 in which a use lower limit pressure is set to multiple levels.

In the example of FIG. 1, the three accumulators 10, 12, and 14configure the multi-stage accumulator 101. In the example of FIG. 1, forexample, the accumulator 10 functions as a 1st bank having a low uselower limit pressure. The accumulator 12 functions as a 2nd bank havingan intermediate use lower limit pressure, for example. The accumulator14 functions as a 3rd bank having a high use lower limit pressure, forexample. However, the present invention is not limited thereto. Theaccumulators used in the 1st bank to the 3rd bank are replaced asneeded.

In the hydrogen station 102, a curdle, an intermediate accumulator,and/or a hydrogen production apparatus (not shown) are also disposed.Further, a hydrogen trailer (not shown) for filling and deliveringhydrogen gas arrives at the inside of the hydrogen station 102.

Further, in FIG. 1, the suction side of the compressor 40 is connectedto the curdle, the intermediate accumulator, the filling tank of thehydrogen trailer, or the hydrogen production apparatus described aboveby a pipe.

The discharge side of the compressor 40 is connected to the accumulator10 via a valve 21 by a pipe. Similarly, the discharge side of thecompressor 40 is connected to the accumulator 12 via a valve 23 by apipe. Similarly, the discharge side of the compressor 40 is connected tothe accumulator 14 via a valve 25 by a pipe.

Further, the accumulator 10 is connected to the dispenser 30 via a valve22 by a pipe. Further, the accumulator 12 is connected to the dispenser30 via a valve 24 by a pipe. Further, the accumulator 14 is connected tothe dispenser 30 via a valve 26 by a pipe. As such, the dispenser 30 iscommonly connected to the accumulators 10, 12, and 14 configuring themulti-stage accumulator 101.

In FIG. 1, a shut-off valve 36, a flow rate adjustment valve 33, aflowmeter 37, a cooler 32 (precooler), a shut-off valve 38, an emergencydetachment coupler 41, and a control circuit 43 are disposed in thedispenser 30. Further, a nozzle 44 extending to the outside of thedispenser 30 is disposed in the dispenser 30. The dispenser 30 sendshydrogen gas (hydrogen fuel) supplied from the multi-stage accumulator101 to the cooler 32 via the shut-off valve 36, the flow rate adjustmentvalve 33, and the flowmeter 37. At that time, a flow rate of thehydrogen fuel supplied from the multi-stage accumulator 101 per unittime is controlled by the flow rate adjustment valve 33, and is measuredby the flowmeter 37. Then, the hydrogen fuel is cooled to, for example,−40° C. by the cooler 32. The cooled hydrogen fuel passes through theshut-off valve 38, the emergency detachment coupler 41, and the nozzle44, and a fuel tank 202 mounted on an FCV 200 is filled with thehydrogen fuel by using a differential pressure. Further, a refrigerantcooled by the refrigerator 42 is circulated in the cooler 32 by acirculation pump (not shown). Further, the control circuit 43 isconfigured to be able to communicate with an on-board device 204 in theFCV 200 (fuel cell vehicle (FCV) powered by the hydrogen fuel) that hasarrived at the hydrogen station 102. For example, the control circuit 43is configured to be able to perform wireless communication usinginfrared rays. Further, the control circuit 43 is connected to thecontrol circuit 100 that controls the entire hydrogen filling system500.

Further, in the hydrogen filling system 500 in FIG. 1, a plurality ofpressure gauges are disposed at different positions in a flow passage ofthe hydrogen fuel between the multi-stage accumulator 101 and an outletof the dispenser 30. Specifically, a pressure in the accumulator 10 ismeasured by a pressure gauge 11. A pressure in the accumulator 12 ismeasured by a pressure gauge 13. A pressure in the accumulator 14 ismeasured by a pressure gauge 15. Further, in the dispenser 30, apressure near an inlet of the dispenser 30 supplied to the dispenser 30is measured by a pressure gauge 27. Further, a pressure near the outletof the dispenser 30 is measured by a pressure gauge 28. In the exampleof FIG. 1, the pressure gauge 27 measures a pressure of the upstreamside (primary side) of the shut-off valve 36 located on the primary sideof the cooler 32. The pressure gauge 28 measures a pressure near theemergency detachment coupler 41 on the secondary side of the cooler 32.Pressure data measured by each pressure gauge is output to the controlcircuit 100 at all times or at a predetermined sampling cycle (forexample, 10 msec to several seconds). In other words, the controlcircuit 100 monitors the pressure measured by each pressure gauge at alltimes or at a predetermined sampling cycle (for example, 10 msec toseveral seconds). Further, a pressure of the fuel tank 202 mounted onthe FCV 200 is measured by a pressure gauge 206 mounted on the FCV 200.As will be described later, the pressure of the fuel tank 202 mounted onthe FCV 200 is monitored at all times or at predetermined samplingintervals (for example, 10 msec to several seconds) while thecommunication between the on-board device 204 and the control circuit 43is established.

Further, in the dispenser 30, a temperature near the outlet of thedispenser 30 of the hydrogen gas supplied to the FCV 200 is measured bya thermometer 29. The thermometer 29 is on the secondary side of thecooler 32, and measures a temperature near the emergency detachmentcoupler 41, for example. Further, an outside air temperature near thedispenser 30 is measured by a thermometer 31. Temperature data measuredby each thermometer is output to the control circuit 100 at all times orat a predetermined sampling cycle (for example, 10 msec to several tensof seconds). In other words, the control circuit 100 monitors thetemperature measured by each thermometer at all times or at apredetermined sampling cycle (for example, 10 msec to several tens ofseconds). Further, a temperature of the fuel tank 202 mounted on the FCV200 is measured by a thermometer 207 mounted on the FCV 200. As will bedescribed later, the temperature of the fuel tank 202 mounted on the FCV200 is monitored at all times or at predetermined sampling intervals(for example, 10 msec to several seconds) while the communicationbetween the on-board device 204 and the control circuit 43 isestablished.

In a state where the hydrogen gas accumulated in the curdle, theintermediate accumulator, or the tank of the hydrogen trailer isdecompressed to a low pressure (for example, 0.6 MPa) by each regulator(not shown) controlled by the control circuit 100, the hydrogen gas issupplied to the suction side of the compressor 40. Similarly, thehydrogen gas produced by the hydrogen production apparatus is suppliedto the suction side of the compressor 40 at a low pressure (for example,0.6 MPa). Under the control of the control circuit 100, the compressor40 supplies the hydrogen gas supplied at low pressure to theaccumulators 10, 12, and 14 of the multi-stage accumulator 101 whilecompressing the hydrogen gas. The compressor 40 performs compressionuntil the internal pressure of each of the accumulators 10, 12, and 14of the multi-stage accumulator 101 becomes a predetermined high pressure(for example, 82 MPa). In other words, the compressor 40 performscompression until a secondary side pressure P_(OUT) of the dischargeside becomes a predetermined high pressure (for example, 82 MPa).Whether a partner supplying the hydrogen gas to the suction side of thecompressor 40 is the curdle, the intermediate accumulator, the hydrogentrailer, or the hydrogen production apparatus may be determined bycontrol of the control circuit 100. Similarly, whether a partner towhich the compressor 40 supplies the hydrogen gas is the accumulator 10,12, or 14 may be determined by controlling opening/closing of thecorresponding valves 21, 23, and 25 disposed on the respective pipes bythe control circuit 100. Alternatively, control may be performed so thatthe hydrogen gas is supplied to two or more accumulators at the sametime.

In the example described above, the case where control is performed sothat a pressure P_(IN) for supplying the hydrogen gas to the suctionside of the compressor 40 is reduced to a predetermined low pressure(for example, 0.6 MPa) has been shown. However, the present invention isnot limited thereto. The hydrogen gas accumulated in the curdle, theintermediate accumulator, or the hydrogen trailer may be supplied to thesuction side of the compressor 40 without reducing the pressure or at apressure higher than a predetermined low pressure (for example, 0.6MPa), and may be compressed.

The hydrogen gas accumulated in the multi-stage accumulator 101 iscooled by the cooler 32 in the dispenser 30 and is supplied from thedispenser 30 to the FCV 200 arriving at the inside of the hydrogenstation 102.

FIG. 2 is a configuration diagram showing an example of an internalconfiguration of the control circuit that controls the entire hydrogenfilling system in the first embodiment. In FIG. 2, a communicationcontrol circuit 50, a memory 51, a reception unit 52, an outside airtemperature reception unit 53, an end pressure calculation unit 54, atimer 55, a temperature difference calculation unit 56, a filling speedcalculation unit 57, a system control unit 58, a determination unit 59,a pressure recovery control unit 61, a supply control unit 63, a bankpressure reception unit 66, dispenser information reception unit 67, anoutput unit 74, a monitor 76, and storage devices 80, 84, and 86 such asmagnetic disk devices are disposed in the control circuit 100. Thepressure recovery control unit 61 has a valve control unit 60 and acompressor control unit 62. The supply control unit 63 has a dispensercontrol unit 64, a valve control unit 65, and a refrigerator controlunit 68. Each “unit” such as the reception unit 52, the outside airtemperature reception unit 53, the end pressure calculation unit 54, thetimer 55, the temperature difference calculation unit 56, the fillingspeed calculation unit 57, the system control unit 58, the determinationunit 59, the pressure recovery control unit 61 (the valve control unit60 and the compressor control unit 62), the supply control unit 63 (thedispenser control unit 64, the valve control unit 65, and therefrigerator control unit 68), the bank pressure reception unit 66, thedispenser information reception unit 67, and the output unit 74 includesa processing circuit, and an electric circuit, a computer, a processor,a circuit board, a semiconductor device or the like is included in theprocessing circuit. Further, a common processing circuit (sameprocessing circuit) may be used for each “unit”. Alternatively, adifferent processing circuit (separate processing circuit) may be used.Input data required in the reception unit 52, the outside airtemperature reception unit 53, the end pressure calculation unit 54, thetimer 55, the temperature difference calculation unit 56, the fillingspeed calculation unit 57, the system control unit 58, the determinationunit 59, the pressure recovery control unit 61 (the valve control unit60 and the compressor control unit 62), the supply control unit 63 (thedispenser control unit 64, the valve control unit 65, and therefrigerator control unit 68), the bank pressure reception unit 66, thedispenser information reception unit 67, and the output unit 74, orcalculated results are stored in the memory 51 each time.

Further, a conversion table 81 showing a correlation between FCVinformation such as the pressure, the temperature, and the volume of thefuel tank 202 mounted on the FCV 200, a remaining amount of the hydrogengas corresponding to the FCV information, and filling information suchas a final pressure and a final temperature for filling the fuel tank202 with the hydrogen gas is stored in the storage device 80. Further, acorrection table 83 for correcting a result obtained from the conversiontable 81 is stored in the storage device 80.

Further, a relation expression parameter 87 between a difference ΔTbetween a maximum allowable temperature Tmax of the fuel tank 202 and aninitial temperature Ti of the fuel tank 202 and a filling speed M isstored in a storage device 86. Further, a relation table 88 between thedifference ΔT between the maximum allowable temperature Tmax of the fueltank 202 and the initial temperature Ti of the fuel tank 202, and thefilling speed M is stored in the storage device 86. The relationexpression parameter 87 and the relation table 88 are created for eachhydrogen gas supply temperature. Further, the relation expressionparameter is created depending on an initial pressure Pa of the fueltank 202. Further, the relation expression parameter is createddepending on an outside air temperature T′. In the example of FIG. 2, acase where both the relation expression parameter 87 and the relationtable 88 are stored is shown, but only one of them may be stored.

Further, the bank pressure reception unit 66 receives the pressuremeasured by each of the pressure gauges 11, 13, and 15 at all times orat a predetermined sampling cycle (for example, 10 msec to severalseconds), and stores the pressure in the storage device 84 together witha reception time. Similarly, the dispenser information reception unit 67receives the pressure measured by each of the pressure gauges 27 and 28in the dispenser 30 at all times or at a predetermined sampling cycle(for example, 10 msec to several seconds), and stores the pressure inthe storage device 84 together with a reception time. Further, thedispenser information reception unit 67 receives the temperaturemeasured by the thermometer 29 in the dispenser 30 at all times or at apredetermined sampling cycle (for example, 10 msec to several seconds),and stores the temperature in the storage device 84 together with thereception time.

As described above, conventionally, in the case of filling the hydrogengas at the hydrogen station 102, a filling time until full filling isestimated by a simulation with a large margin in advance for an actualtemperature increase of the fuel tank 202 so that the temperature of thefuel tank 202 of the FCV 200 does not become a high temperature, byusing the hydrogen gas that is cooled enough to prevent the supplytemperature of the hydrogen gas from increasing. Then, a filling speedis determined according to the estimated filling time. Therefore, thedetermined filling speed is generally set lower as compared with theactual filling capacity of the hydrogen station 102. Therefore, in thefirst embodiment, a correlation between a difference between a maximumallowable temperature of the fuel tank 202 and an initial temperature ofthe fuel tank 202, and a filling speed is calculated on the basis ofdata when the hydrogen gas is actually filled into the fuel tank 202 ofthe FCV 200 at the hydrogen station 102, and the filling speed isdetermined according to the correlation. Hereinafter, it will bespecifically described.

FIG. 3 is a flowchart showing main steps of a hydrogen filling method inthe first embodiment. In FIG. 3, the hydrogen filling method in thefirst embodiment executes a series of steps such as a nozzle connectionstep (S102), a refrigerator circulation start step (S104), an FCVinformation reception step (S106), an outside air temperature receptionstep (S108), an end pressure calculation step (S110), a temperaturedifference calculation step (S112), a filling speed calculation step(S114), a hydrogen filling step (S116), a determination step (S118), ahydrogen supply temperature input step (S120), and a refrigeratorcirculation stop and pressure recovery continuation step (S122).

As the nozzle connection step (S102), when the FCV 200 arrives at thehydrogen station 102, a worker of the hydrogen station 102 or a user ofthe FCV 200 connects (fits) the nozzle 44 of the dispenser 30 to areception port (receptacle) of the fuel tank 202 of the FCV 200, andfixes the nozzle 44. When the FCV 200 arrives at the inside of thehydrogen station 102 and the nozzle 44 of the dispenser 30 is connectedand fixed to the reception port (receptacle) of the fuel tank 202 of theFCV 200 by the user or the worker of the hydrogen station 102,communication between the on-board device 204 and the control circuit 43(relay device) is established.

As the refrigerator circulation start step (S104), when thecommunication between the on-board device 204 and the control circuit 43(relay device) is established, the refrigerator control unit 68 in thecontrol circuit 100 controls the refrigerator 42 via the communicationcontrol circuit 50 and drives a circulation pump of the refrigerator 42.In this way, the circulation of the refrigerant between the refrigerator42 and the cooler 32 is started. As a result, cooling of the hydrogengas is started by the cooler 32 in the dispenser 30. As described above,the hydrogen gas is cooled by the cooler 32 disposed in the dispenser30. However, in the first embodiment, when the filling of the hydrogengas into the fuel tank 202 is started, cooling of the hydrogen gas isstarted by the cooler 32 in the dispenser 30, and the circulation of therefrigerant is stopped when the filling of the hydrogen gas into thefuel tank 202 is completed, as described later. As described above,conventionally, the circulation pump that is constantly driven by theconstant circulation is stopped during a period in which the hydrogengas is not filled. As a result, it is possible to reduce the consumptionof an amount of electric power for driving the circulation pump, whichhas occurred during the period in which the hydrogen gas is not filled.

As the FCV information reception step (S106), the reception unit 52receives the temperature (initial temperature) Ti of the fuel tank 202before the start of filling from the FCV 200 (fuel cell vehicle: FCV)equipped with the fuel tank 202 filled with the hydrogen gas and poweredby the hydrogen gas. Further, when the reception unit 52 receives thetemperature Ti of the fuel tank 202 before the start of filling, thereception unit 52 also receives the pressure (initial pressure) Pa ofthe fuel tank 202 before the start of filling. Specifically, thereception unit 52 receives FCV information regarding the fuel tank 202(hydrogen storage container) mounted on the FCV 200 from the on-boarddevice 204 mounted on the FCV 200 (fuel cell vehicle (FCV)) powered bythe hydrogen gas. Specifically, the following operation is performed.When the communication between the on-board device 204 and the controlcircuit 43 (relay device) is established, the FCV information such asthe present pressure and temperature of the fuel tank 202 and the volumeof the fuel tank 202 is output (transmitted) in real time from theon-board device 204. The FCV information is relayed by the controlcircuit 43 and transmitted to the control circuit 100. In the controlcircuit 100, the reception unit 52 receives the FCV information via thecommunication control circuit 50. The FCV information is monitored atall times or at predetermined sampling intervals (for example, 10 msecto several seconds) while the communication between the on-board device204 and the control circuit 43 is established. The received FCVinformation is stored in the storage device 80 together with receptiontime information.

As the outside air temperature reception step (S108), the outside airtemperature reception unit 53 receives the outside air temperature T′measured by the thermometer 31 via the communication control circuit 50.The received information on the outside air temperature T′ is stored inthe storage device 80 together with reception time information.

As the end pressure calculation step (S110), the end pressurecalculation unit 54 reads the conversion table 81 from the storagedevice 80, and calculates and predicts a final pressure PF correspondingto the pressure Pa, temperature Ti, and volume V of the fuel tank 202 atthe time of initial reception and the outside air temperature T′, whichhave been received. Further, the end pressure calculation unit 54 readsthe correction table 83 from the storage device 80, and corrects anumerical value obtained by the conversion table 81. When only data ofthe conversion table 81 has a large error in an obtained result, thecorrection table 83 may be provided on the basis of a result obtained byan experiment, a simulation or the like. The calculated final pressurePF is output to the system control unit 58.

In the temperature difference calculation step (S112), the temperaturedifference calculation unit 56 calculates a difference ΔT (=Tmax−Ti)between the preset maximum temperature Tmax and the temperature (initialtemperature) Ti of the fuel tank 202. For example, 85° C. is preset asthe maximum temperature Tmax allowed in the fuel tank 202. When thereceived temperature (initial temperature) Ti of the fuel tank 202before filling is, for example, 15° C., the difference ΔT=85−15=70° C.is calculated.

FIG. 4 is a diagram showing an example of a correlation between thetemperature increase change of the fuel tank and the filling speed inthe first embodiment. In FIG. 4, a vertical axis indicates thedifference ΔT (° C.) between the preset maximum temperature Tmax and thetemperature (initial temperature) Ti of the fuel tank 202 as thetemperature increase change. A horizontal axis indicates the fillingspeed M (MPa/min). Further, the correlation is created for each hydrogengas supply temperature. Furthermore, the correlation depends on thepressure (initial pressure) Pa before the start of filling of the fueltank 202 and the outside air temperature T′. Therefore, the correlationis created for each combination of the initial pressure Pa of the fueltank 202 and the outside air temperature T′ and for each hydrogen gassupply temperature. In the example of FIG. 4, correlations are shown forhydrogen gas supply temperatures of −20° C., −26° C., −32° C., and −38°C. The correlation is created on the basis of data when the hydrogen gasis actually filled at the hydrogen station 102. Therefore, aconventional margin is not included in the correlation. In the exampleof FIG. 4, a graph in which a plotted relation is approximated by aquadratic polynomial is shown.

FIG. 5 is a diagram illustrating a coefficient table of a quadraticpolynomial when the correlation between the temperature increase changeof the fuel tank and the filling speed is approximated by the quadraticpolynomial in the first embodiment. In FIG. 5, values of coefficients a,b, and c of the quadratic polynomial described in FIG. 4 are defined foreach hydrogen gas supply temperature. In the example of FIG. 5, a casewhere the coefficients a, b, and c of the quadratic polynomial aredefined for hydrogen gas supply temperatures of −20° C., −23° C., −26°C., −29° C., −32° C., −35° C., and −38° C. is shown. Hydrogen gas supplytemperatures that are not shown in the correlation equation of FIG. 4may be obtained by linear interpolation. Further, when hydrogen gassupply temperatures at the time of actual calculation are not defined,linearly interpolated values may be used. The correlation between thedifference between the maximum allowable temperature and the initialtemperature of the fuel tank, and the filling speed is not limited tothe quadratic equation. The correlation may be approximated by equationsof other orders.

FIG. 6 is a diagram showing another example of the correlation betweenthe temperature increase change of the fuel tank and the filling speedin the first embodiment. In FIG. 6, a vertical axis indicates thedifference ΔT (° C.) between the preset maximum temperature Tmax and thetemperature (initial temperature) Ti of the fuel tank 202 as thetemperature increase change. A horizontal axis indicates the fillingspeed M (MPa/min). Further, the correlation is created for each hydrogengas supply temperature, similarly to the case shown in FIG. 4.Furthermore, the correlation depends on the pressure (initial pressure)Pa before the start of filling of the fuel tank 202 and the outside airtemperature T′, similarly to the case shown in FIG. 4. Therefore, thecorrelation is created for each combination of the initial pressure Paof the fuel tank 202 and the outside air temperature T′ and for eachhydrogen gas supply temperature. In the example of FIG. 6, correlationsare shown for hydrogen gas supply temperatures of −23° C., −29° C., and−35° C. The correlation is created on the basis of data when thehydrogen gas is actually filled at the hydrogen station 102. Therefore,a conventional margin is not included in the correlation. In the exampleof FIG. 6, a graph in which a plotted relation is approximated by acubic polynomial is shown.

FIG. 7 is a diagram illustrating a coefficient table of a cubicpolynomial when the correlation between the temperature increase changeof the fuel tank and the filling speed is approximated by the cubicpolynomial in the first embodiment. In FIG. 7, values of coefficients A,B, C, and D of the cubic polynomial described in FIG. 6 are defined foreach hydrogen gas supply temperature. In the example of FIG. 7, a casewhere the coefficients A, B, C, and D of the cubic polynomial aredefined for hydrogen gas supply temperatures of −20° C., −23° C., −26°C., −29° C., −32° C., −35° C., and −38° C. is shown. Hydrogen gas supplytemperatures that are not shown in the correlation equation of FIG. 6may be obtained by linear interpolation. Further, when hydrogen gassupply temperatures at the time of actual calculation are not defined,linearly interpolated values may be used.

In FIGS. 4 to 7, the relation expression between the temperatureincrease change of the fuel tank 202 and the filling speed is shown, butthe relation may be defined as a relation table instead of thecoefficient table. The relation table may also be created for eachcombination of the initial pressure Pa of the fuel tank 202 and theoutside air temperature T′ and for each hydrogen gas supply temperature.

As the filling speed calculation step (S114), the filling speedcalculation unit 57 calculates the filling speed M of the hydrogen gasthat depends on the difference ΔT. The filling speed M is calculated byusing the above-described relation expression or relation table betweenthe temperature increase change of the tank depending on the supplytemperature of the hydrogen gas supplied via the dispenser 30 and thefilling speed. Specifically, first, a coefficient table or a relationtable of a relation expression corresponding to the initial pressure Paof the fuel tank 202, the outside air temperature T′, and the presethydrogen gas supply temperature T″ is read from the storage device 86.Since the refrigerant is not supplied from the refrigerator 42 to thecooler 32 before the start of filling, the hydrogen gas is not alwayssufficiently cooled. Therefore, the initial value T″ of the hydrogen gassupply temperature may be preset. For example, the initial value T″=−20°C. is set. When the circulation of the refrigerant is started, thehydrogen gas is cooled in a short period. For example, it is cooled inseveral tens of seconds. For this reason, until then, a temporaryfilling speed may be calculated with the initial value T″. Therefore,the filling speed calculation unit 57 calculates the filling speed Mcorresponding to the calculated difference ΔT by referring to thecoefficient table or the relation table of the read relation expression.The calculated filling speed M is output to the system control unit 58.

As the hydrogen filling step (S116), the hydrogen gas is filled into thefuel tank 202 at the calculated filling speed M from the multi-stageaccumulator 101 (accumulator) in which the hydrogen gas has beenaccumulated via the dispenser 30. In other words, the dispenser 30 fillsthe fuel tank 202 with the hydrogen gas at the calculated filling speedM from the multi-stage accumulator 101 (accumulator).

FIG. 8 is a diagram illustrating a filling method in a case ofperforming differential pressure filling of the hydrogen fuel by usingthe multi-stage accumulator in the first embodiment. In FIG. 8, avertical axis indicates a pressure and a horizontal axis indicates atime. In the case of performing the differential pressure filling of thehydrogen fuel on the FCV 200, generally, the hydrogen fuel isaccumulated in the accumulators 10, 12, and 14 of the multi-stageaccumulator 101 in advance at the same pressure PO (for example, 82MPa). On the other hand, the pressure of the fuel tank 202 of the FCV200 that has arrived at the hydrogen station 102 becomes a pressure Pa.A case where filling starts for the fuel tank 202 of the FCV 200 fromthe above state will be described.

First, the filling starts from the 1st bank, for example, theaccumulator 10 to the fuel tank 202. Specifically, the followingoperation is performed. Under the control of the system control unit 58,the supply control unit 63 controls the supply unit 106, and suppliesthe hydrogen fuel from the accumulator 10 to the fuel tank 202 of theFCV 200. Specifically, the system control unit 58 controls the dispensercontrol unit 64 and the valve control unit 65. The dispenser controlunit 64 communicates with the control circuit 43 of the dispenser 30 viathe communication control circuit 50, and controls the operation of thedispenser 30. Specifically, first, the control circuit 43 adjusts theopening of the flow rate adjustment valve in the dispenser 30 so that afilling speed becomes the calculated filling speed M. Next, the controlcircuit 43 opens the shut-off valves 36 and 38 in the dispenser 30.Then, the valve control unit 65 outputs a control signal to the valves22, 24, and 26 via the communication control circuit 50, and controlsopening/closing of each valve. Specifically, the valve 22 is opened andthe valves 24 and 26 are kept closed. As a result, the hydrogen fuel issupplied from the accumulator 10 to the fuel tank 202. By thedifferential pressure between the accumulator 10 and the fuel tank 202,the hydrogen fuel accumulated in the accumulator 10 moves to the side ofthe fuel tank 202 at the adjusted filling speed, and the pressure of thefuel tank 202 gradually increases as indicated by a dotted line Pt.Accordingly, the pressure (graph indicated by “1st”) of the accumulator10 gradually decreases. Then, at a point of time when a pressure fallsoutside a use lower limit pressure of the 1st bank and a time T1 elapsesfrom the start of filling, an accumulator to be used is switched fromthe accumulator 10 to the 2nd bank, for example, the accumulator 12.Specifically, the valve control unit 65 outputs a control signal to thevalves 22, 24, and 26 via the communication control circuit 50, andcontrols opening/closing of each valve. Specifically, the valve 24 isopened, the valve 22 is closed, and the valve 26 is kept closed. As aresult, since the differential pressure between the accumulator 12 andthe fuel tank 202 increases, the filling speed can be kept high.

Then, by the differential pressure between the 2nd bank, for example,the accumulator 12 and the fuel tank 202, the hydrogen fuel accumulatedin the accumulator 12 moves to the side of the fuel tank 202 at the sameadjusted filling speed, and the pressure of the fuel tank 202 graduallyincreases as indicated by the dotted line Pt. Accordingly, the pressure(graph indicated by “2nd”) of the accumulator 12 gradually decreases.Then, at a point of time when a pressure falls outside a use lower limitpressure of the 2nd bank and a time T2 elapses from the start offilling, an accumulator to be used is switched from the accumulator 12to the 3rd bank, for example, the accumulator 14. Specifically, thevalve control unit 65 outputs a control signal to the valves 22, 24, and26 via the communication control circuit 50, and controlsopening/closing of each valve. Specifically, the valve 26 is opened, thevalve 24 is closed, and the valve 22 is kept closed. As a result, sincethe differential pressure between the accumulator 14 and the fuel tank202 increases, the filling speed can be kept high.

Then, by the differential pressure between the 3rd bank, for example,the accumulator 14 and the fuel tank 202, the hydrogen fuel accumulatedin the accumulator 14 moves to the side of the fuel tank 202 at theadjusted filling speed, and the pressure of the fuel tank 202 graduallyincreases as indicated by the dotted line Pt. Accordingly, the pressure(graph indicated by “3rd”) of the accumulator 14 gradually decreases.Then, filling is performed until the pressure of the fuel tank 202becomes the calculated final pressure PF (for example, 65 to 81 MPa) bythe accumulator 14 to be the 3rd bank.

As described above, the fuel tank 202 is filled with the hydrogen gas inorder from the 1st bank. As long as the hydrogen gas is filled at thecalculated filling speed M, the temperature of the fuel tank 202increases only to the maximum temperature Tmax even if it increases fromthe temperature (initial temperature) Ti of the fuel tank 202. In otherwords, the temperature of the fuel tank 202 does not exceed the maximumtemperature Tmax as long as the hydrogen gas is filled at the calculatedfilling speed M. However, such a relation holds unless the hydrogen gassupply temperature changes. For the outside air temperature, a changeduring a filling period of about several minutes may be regarded as anerror level. Therefore, the filling speed M is reviewed on a regularbasis.

As the determination step (S118), the determination unit 59 determineswhether the filling has been completed. Specifically, the determinationunit 59 determines whether the pressure in the fuel tank 202 has reachedthe calculated final pressure PF each time the time set in the timer 55has elapsed. When the filling has been completed, the process proceedsto the refrigerator circulation stop step (S122) and the pressurerecovery step (S124). When the filling has not been completed yet, theprocess proceeds to the hydrogen supply temperature input step (S120).The time set in the timer 55 is set to several tens of seconds (forexample, 30 seconds) for the first filling immediately after the startof filling, and is set to several seconds (for example, 5 seconds) forthe second and subsequent fillings. In the first embodiment, since therefrigerant is circulated from the refrigerator 42 to the cooler 32 eachtime the hydrogen gas is filled, the cooling of the hydrogen gas at thestart of filling may be insufficient. Therefore, the time in the firstfilling is preferably set longer than the times in the second andsubsequent fillings by considering a time required for cooling thehydrogen gas by the cooler 32.

As the hydrogen supply temperature input step (S120), the filling speedcalculation unit 57 inputs the present hydrogen supply temperature.Specifically, the latest temperature measured by the thermometer 29stored in the storage device 84 is input as the latest hydrogen supplytemperature. Then, the process returns to the filling speed calculationstep (S114), and the steps from the filling speed calculation step(S114) to the hydrogen supply temperature input step (S120) are repeateduntil the filling is completed.

In the filling speed calculation step (S114), the filling speedcalculation unit 57 reads, from the storage device 86, a coefficienttable or a relation table of a relation expression corresponding to thelatest hydrogen supply temperature, the measured outside air temperatureT′, and the obtained initial pressure Pa of the fuel tank 202. Then, thefilling speed calculation unit 57 refers to the read coefficient tableor relation table of the relation expression, and recalculates thefilling speed M corresponding to the calculated difference ΔT. Here,only the hydrogen supply temperature is changed, and the otherparameters are used without being changed. Then, the calculated fillingspeed M is output to the system control unit 58. Then, each time thefilling speed M is calculated, the opening of the flow rate adjustmentvalve 33 is readjusted so that a filling speed becomes the recalculatedfilling speed M. Then, each time the filling speed M is calculated, thehydrogen gas filling operation is continued at the readjusted fillingspeed M.

As the refrigerator circulation stop and pressure recovery continuationstep (S122), when the filling is completed, the refrigerator controlunit 68 controls the refrigerator 42 via the communication controlcircuit 50, and stops the circulation pump of the refrigerator 42. Inthis way, the circulation of the refrigerant between the refrigerator 42and the cooler 32 is stopped. As a result, the cooling of the hydrogengas by the cooler 32 in the dispenser 30 is stopped or the cooling speedis reduced. In the first embodiment, since the filling speed Mcorresponding to the actual temperature difference ΔT depending on theactual hydrogen supply temperature, the actual outside air temperature,and the actual initial pressure is used, it is possible to cope with thechange in the hydrogen supply temperature. For this reason, it ispossible to eliminate the need to cool the hydrogen gas excessively bythe cooler 32 constantly. Therefore, the circulation pump that isconstantly driven by the constant circulation in the past can be stoppedduring a period in which the hydrogen gas is not filled. As a result, itis possible to reduce electric power for driving the circulation pump,which has occurred during the period in which the hydrogen gas is notfilled.

In the above-described example, cooling of the hydrogen gas is startedby the cooler 32 in the dispenser 30 when the filling of the hydrogengas into the fuel tank 202 is started, and the circulation of therefrigerant is stopped when the filling of the hydrogen gas into thefuel tank 202 is completed. However, the present invention is notlimited thereto. The circulation amount of the refrigerant to the cooler32 may be increased when the filling of the hydrogen gas into the fueltank 202 is started, and the circulation amount of the refrigerant maybe reduced when the filling of the hydrogen gas into the fuel tank 202is completed. Even with such a configuration, the electric power fordriving the circulation pump can be reduced.

Further, the pressure recovery mechanism 104 recovers the pressure ofeach of the accumulators 10, 12, and 14. The compressor 40 and thevalves 21, 23, and 25 configure the pressure recovery mechanism 104.First, the system control unit 58 selects a supply source of thehydrogen fuel to be connected to the suction side of the compressor 40from the curdle, the intermediate accumulator, the hydrogen trailer, orthe hydrogen production apparatus (not shown). Then, under the controlof the system control unit 58, the pressure recovery control unit 61controls the pressure recovery mechanism 104, and recovers the pressureof each of the accumulators 10, 12, and 14. Specifically, the followingoperation is performed. In the accumulator of each bank used for fillingthe fuel tank 202 of the FCV 200, the pressure may also be recoveredduring filling. However, since there is not enough time to recover thepressure to a prescribed pressure, the pressure should be recoveredafter filling. Since the 1st bank, the 2nd bank, and the 3rd bank areswitched in this order, first, the pressure of the accumulator 10 to bethe 1st bank is recovered. The valve control unit 60 opens the valve 21from a state where the valves 21, 23, and 25 are closed.

Then, the compressor control unit 62 drives the compressor 40, sends thehydrogen fuel of the low pressure (for example, 0.6 MPa) from the supplysource of the hydrogen fuel while compressing the hydrogen fuel, andfills the accumulator 10 with the hydrogen fuel until the pressure ofthe accumulator 10 becomes a predetermined pressure PO (for example, 82MPa), thereby recovering the pressure of the accumulator 10.

Next, the valve control unit 60 closes the valve 21, and opens the valve23 instead.

Then, the compressor control unit 62 drives the compressor 40, sends thehydrogen fuel of the low pressure (for example, 0.6 MPa) whilecompressing the hydrogen fuel, and fills the accumulator 12 with thehydrogen fuel until the pressure of the accumulator 12 becomes thepredetermined pressure PO (for example, 82 MPa), thereby recovering thepressure of the accumulator 12.

Next, the valve control unit 60 closes the valve 23, and opens the valve25 instead.

Then, the compressor control unit 62 drives the compressor 40, sends thehydrogen fuel of the low pressure (for example, 0.6 MPa) whilecompressing the hydrogen fuel, and fills the accumulator 14 with thehydrogen fuel until the pressure of the accumulator 14 becomes thepredetermined pressure PO (for example, 82 MPa), thereby recovering thepressure of the accumulator 14.

In this way, even when the next FCV 200 arrives at the hydrogen station102, the hydrogen fuel can be supplied similarly.

As described above, according to the first embodiment, when the hydrogengas is filled, the hydrogen gas can be filled at the filling speed Mwhere the extra margin is eliminated Therefore, a filling time can beshortened. Further, the circulation pump is stopped during the periodwhen the hydrogen gas is not filled. As a result, it is possible toreduce electric power for driving the circulation pump, which hasoccurred during the period in which the hydrogen gas is not filled.

The embodiment has been described with reference to the specificexamples. However, the present invention is not limited to thesespecific examples. For example, in the above-described examples, thecase where the multi-stage accumulator 101 including the threeaccumulators 10, 12, and 14 is used to fill one FCV with the hydrogenfuel has been described. However, the present invention is not limitedthereto. According to the volumes of the accumulators 10, 12, and 14 andthe like, more accumulators may be used for filling of one FCV.Alternatively, two accumulators may be used for filling of one FCV.

Further, descriptions of parts and the like that are not directlynecessary for explanation of the present invention, such as the deviceconfiguration and the control method, are omitted. However, thenecessary device configuration and control method can be appropriatelyselected and used.

In addition, all hydrogen gas filling methods and hydrogen gas fillingdevices, which include the elements of the present invention and arecapable of being appropriately changed in design by those skilled in theart, are included in the scope of the present invention.

1. A hydrogen gas filling method comprising: receiving, from a vehicleequipped with a tank to be filled with hydrogen gas and powered by thehydrogen gas, a temperature of the tank before a start of filling;calculating a difference between a preset maximum temperature and thetemperature of the tank; calculating a filling speed of the hydrogen gasdepending on the difference; and filling the hydrogen gas from anaccumulator in which the hydrogen gas is accumulated into the tank atthe filling speed calculated via a measuring machine.
 2. The methodaccording to claim 1, wherein the filling speed is calculated by using arelation expression or a relation table between the difference dependingon a supply temperature of the hydrogen gas supplied via the measuringmachine and a filling speed.
 3. The method according to claim 2, whereinthe relation expression is an approximate expression in which acorrelation between the difference and a filling speed is represented bya polynomial of second order or higher.
 4. The method according to claim1, wherein when the temperature of the tank before the start of fillingis received, a pressure of the tank before the start of filling is alsoreceived, and the filling speed depends on the pressure of the tankbefore the start of filling.
 5. The method according to claim 1, whereinthe filling speed depends on an outside air temperature.
 6. The methodaccording to claim 1, wherein the hydrogen gas is cooled by a coolerdisposed in the measuring machine, and when the filling of the hydrogengas into the tank is started, circulation of a refrigerant to the cooleris started, and when the filling of the hydrogen gas into the tank iscompleted, the circulation of the refrigerant is stopped.
 7. The methodaccording to claim 1, wherein the hydrogen gas is cooled by a coolerdisposed in the measuring machine, when the filling of the hydrogen gasinto the tank is started, a circulation amount of a refrigerant to thecooler is increased, and when the filling of the hydrogen gas into thetank is completed, the circulation amount of the refrigerant is reduced.8. The method according to claim 1, wherein the filling speed is changedaccording to a supply temperature of the hydrogen gas during the fillingof the hydrogen gas into the tank.
 9. A hydrogen gas filling devicecomprising: a reception circuit configured to receive, from a vehicleequipped with a tank to be filled with hydrogen gas and powered by thehydrogen gas, a temperature of the tank before a start of filling; adifference calculation circuit configured to calculate a differencebetween a preset maximum temperature and the temperature of the tank; afilling speed calculation circuit configured to calculate a fillingspeed of the hydrogen gas depending on the difference; an accumulatorconfigured to accumulate hydrogen gas; and a measuring machineconfigured to fill hydrogen gas from the accumulator into the tank atthe filling speed calculated.